This invention relates to a fuel supplying system for internal combustion engines and more particularly to an improved charge forming device for engines and particularly those of the two-cycle type.
As is well known, it is the practice to provide additional fuel to an internal combustion engine to assist in cold starting. Additional fuel is required under these conditions since the engine and its major components are cold and the low temperature causes fuel condensation which, unless compensated for, can result in a too lean mixture for good starting or cold running. This problem is particularly acute in connection with two-cycle, crankcase compression engines where the fuel/air charge is introduced into the crankcase and is subsequently transferred to the combustion chamber through one or more transfer passages during the piston reciprocation. Because of the long route of travel from the crankcase to the combustion chamber for the fuel air mixture, the condensation problems at low temperatures become particularly acute.
It has also been proposed to run two-cycle, crankcase compression engines on fuels having lower quality that gasoline. Alcohol and kerosene are typical of such low quality fuels on which two-cycle engines have been operated. However, when using these lower quality fuels, it has been the practice to provide a richer fuel such as gasoline for priming and cold starting. However, the priming systems previously employed had the fuel discharge into the engine induction system at a point where the discharge is exposed to a high engine vacuum condition. Thus, this high vacuum can cause excess of the higher quality fuel to be drawn into the engine at times when it is unnecessary and thus offset the disadvantages of running on low quality fuel.
It is, therefore, a principal object of this invention to provide an improved priming system for an internal combustion engine.
It is a further object of this invention to provide an engine priming system wherein the priming fuel will not be depleted during normal engine running.
It is a yet further object of this invention to provide a priming system for an internal combustion engine wherein the discharge of the priming fuel is so located that the priming fuel will not be depleted during normal running.
As has been noted, the problems of fuel condensation in crankcase compress, two-cycle engines at low temperatures are well known. In order to offset these deficiencies and to provide better running under all conditions, it has been proposed to provide a charge forming device which delivers a fuel/air mixture directly into the crankcase and a further charge forming device that delivers a fuel/air mixture into the transfer passage. By providing additional fuel/air discharge into the transfer passage, the likelihood of fuel condensation and the necessity for further enrichment under low temperatures can be minimized. Recently, it has also been proposed to provide cold running enrichment in the charge forming device which supplies the transfer passage. Although the use of two such charge forming devices and the incorporation of cold running enrichment in the one that serves the transfer passage has many advantages, it tends to complicate the engine fuel system in view of the fact that two separate charge forming devices are provided for each chamber of the engine.
It is, therefore, a further object of this invention to provide a compound yet simplified charge forming system for a two-cycle internal combustion engine.
It is another object of this invention to provide a charge forming system for a two-cycle internal combustion engine wherein a plurality of charge formers share a common fuel source.
One very popular application for two-cycle internal combustion engines is in connection with outboard motors. Because of the relative simplicity of the two-cycle engine and its relatively high specific output, it has been the common practice to employ two-cycle engines as the powering device of an outboard motor. The above comments with respect to the design characteristics of the induction system and charge forming device for two-cycle engines apply very strongly to outboard motors. However, with an outboard motor, there is an additional factor to be considered. That is, the engine is frequently positioned in an orientation other than that in which it is designed to normally operate. For example, outboard motors are provide with an arrangement wherein they can be tilted about a horizontally extending axis from a normal running condition to a tilted up out of the water condition. In addition, outboard motors, particularly those of smaller displacements, are frequently detached from the associated watercraft and stored in a horizontally extending position. When this is done, there is a likelihood of leakage of the fuel from the charge former which, obviously, is an undesirable situation. This problem is particularly acute when the engine is provided with separate charge formers for both the crankcase and transfer passages. When such multiple charge formers are used, it is difficult to insure that the design of each charge former is such that fuel cannot be discharged when the engine is oriented other than in its normal running condition.
It is, therefore, a further object of this invention to provide an improved charge forming device for a two-cycle engine that will minimize the likelihood of fuel leakage when the engine is positioned in other than its normal orientation.
It is a further object of this invention to provide an improved charge forming system for a two-cycle internal combustion engine that will minimize the likelihood of fuel leakage.
As has already been noted, there are advantages in connection with two-cycle, crankcase compression internal combustion engines to providing the cold starting and cold running enrichment directly to the transfer passage of the engine. Although devices have been proposed for this purpose, such as that shown in the copending application Ser. No. 631,858, filed Jul. 18, 1984 and entitled "Fuel Supply Device Of A Two-Stroke Engine For An Outboard Motor", filed in the name of Hidekazu Takayashu, and assigned to the assignee of this application, such devices have taken the form of conventional cold starting enrichments found in conventional type of carburetors. Although such arrangements are practical, they are in some instances more complicated than are required for the functions which they serve. This is particularly true, when the main fuel/air requirements are supplied by a separate charge former to the crankcase.
It is, therefore, a further object of this invention to provide an improved and simplified cold starting enrichment device for a two-cycle crankcase compression internal combustion engine.
It is a yet further object of this invention to provide an improved simplified and yet fully adjustable cold starting enrichment device for a two-cycle internal combustion engine.